1. Field of the Invention:
This invention relates to a painting gun used for electrostatic painting, and more particularly, to an improvement in configurations of the painting gun.
2. Discussion of the Background:
Recently, the ratio of painting processes employing robots utilized has shown a sharp increase in the manufacturing processes of automobiles and similarly complex machines. This has the object of organizing painting operations and improving painting qualities. The electrostatic painting method has been employed in the manufacturing processes because the method has the advantages of offering decreased paint loss and providing improved wettability.
As for electrostatic painting guns, a few of them have been developed especially for robots. For many cases, an electrostatic painting gun used by a human operator, disclosed in Japanese Published Unexamined Patent Application No. 244358/1985, and an electrostatic painting gun for reciprocating painting are used without modification in the above mentioned painting processes. As for an electrostatic painting gun especially developed for robot application, TRP-402.TM. manufactured by Thermes Co. is well known and is shown in FIG. 11.
It is known that the center axis of a painting gun nozzle opening should be held perpendicular to the surface of an object to be painted for performing quality painting. However, the conventional type of electrostatic painting hand gun and the electrostatic painting gun for reciprocating painting have straight configurations in which the nozzle opening coincides with the center axis of the gun, and the guns have supply hoses, such as a paint hose, an air hose, etc., extending from their outer surfaces. Accordingly, the guns and the hoses come into contact with an object to be painted when painting minute places Z as shown in FIGS. 8 to 10 with said guns being supported by a robot wrist. As a result, the painting quality at such places is deteriorated, or painting can not be performed at such places in the worst cases, because it is hard to hold the gun in the optimum posture perpendicular to the surface of an object to be painted. Thus, additional painting by a human operator is required for the minute places before or after the painting performed by a robot.
The TRP-402.TM. gun shown in FIG. 11 is known to be useful for solving such problems to a certain degree. The electrostatic painting gun comprises a gun 100 and a bracket 101 installed on the gun at a predetermined angle. A high voltage generator and a paint regulator are built-in to the bracket 101. In addition, hoses 102 for supplying a paint, air and power are built-in to the bracket 101 and a robot wrist 200.
However, it is inevitable that the size of the bracket 101 becomes larger in the above-noted type electrostatic painting gun. Thus, the minute places which are hard to reach can not be painted properly, and it is difficult to clean the electrostatic painting gun. Further, it is difficult to teach painting operations to the robot because the nozzle opening is disposed away from the center axis of the robot wrist center axis. Furthermore, application of the electrostatic painting gun has been limited to a robot having a wrist which can store the hoses within the wrist.